The invention relates to an axial piston motor.
On traditional axial piston motors of the type involved, such as are described e.g. in German patent No. 3,714,888, a control cylinder with control piston assembly is provided to which actuating pressure can be applied and having a displaceable part which is connected with the actuator of the axial piston motor. The control cylinder with control piston assembly is of a circular design and is disposed about a cylindrical drum. The control cylinder here has an annular space containing a bush which is spring-loaded on one side and can have pressure medium applied to its other side, and which cooperates with a cradle having a skew plate. If pressure medium is applied to the annular space, the bush moves against the force of the spring and displaces the cradle, together with the skew plate, from its effective position to its ineffective operating position. This happens independently of the instantaneous power of the drive unit. It is a consequence of this that the axial piston motor does not work unconditionally, and not always in its optimum operating range and thus does not achieve optimum efficiency.
Axial piston motors are also known from German patents Nos. 3,135,605; 3,346, 000 and German published application No. 1,947,641. The main problem improved by the present invention is not recognized in the aforementioned prior art and no measures are there proposed by means of which this problem could be solved.
For example, the adjusting device of German patent No. 3,135,605 has at least one control cylinder with a control piston, to which actuating pressure can be applied and which cooperates with the skew plate. The control piston cooperates with at least one spring body acting in the axial direction of the control cylinder. The control piston is configured as an open hollow cylinder, and its closed end face is connected under pressure with the spring body. The control piston has an auxiliary piston provided with a spring plate while arranged between the end face and the plate of the spring body which presses the spring plate away from the end face.
The spring plate is disposed here in its one operating position outside the control piston and coincides in its other operating position with the open end face of the control piston. It is also known from German published patent application ser. No. 1,947,641, that in the effective position of the skew plate at least one spring body is compressed, and the spring body is configured as a helical spring.
Finally, from German patent No. 3,346,000 it is known to provide at least two control cylinders which are disposed symmetrically with respect to the axis of rotation of the drive device.
It is an object of the present invention to eliminate the above drawback.
In an axial piston motor having a drive shaft, an inclined plate, and an adjusting device for the inclined plate, and at least one adjusting control cylinder with control piston adapted to establish pressure contact and to cooperate with the inclined plate and having a closed face and being formed as an inwardly open cylinder having an open end, a coil spring disposed within the inwardly open cylinder and pressing against the closed face, a sliding bush having two ends, one end thereof ranging into the inwardly open cylinder and having a flange at its opposite end, one end of the coil spring resting against the flange, with the coil spring biasing the flange away, the improvement which comprises a rod connected to the closed face of the control piston, and the sliding bush being formed as a hollow cylindrical sliding object having an inside diameter guided upon the rod.
The invention is realized by an axial piston motor, the efficiency of which is optimised by a control device, by the inclination of the skew plate being adjusted to the instantaneous power of the drive device. This adjustment is suitably automatically carried out.
A particularly expedient embodiment of the present invention provides for the adjusting device to have at least one control cylinder with control piston to which actuating pressure can be applied and which cooperates with the skew plate, and which preferably co-operates with at least one spring body acting in the axial direction of the control cylinder. In this inventive idea it is expedient if at least one spring body is compressed in the effective position of the skew plate. Moreover, a suitable embodiment of the invention provides for the control piston to be configured as a hollow cylinder which is inwardly open and the closed end face of which is connected under pressure with the spring body. The control piston can here be an inward directed coaxial rod, with a hollow cylindrical slide bush which can be displaced on the rod and with a flange disposed on its free end and the spring body between the end face and the flange. The spring body presses the flange away from the end face. This way a control cylinder with control piston assembly is obtained with maximum stroke movements and with minimum dimensions.
In a further suitable embodiment of the invention the slide bush is configured open on both sides and carries the spring body. Provision can here be made for the free end of the rod, which has a circular cross section, to bear a collar which is larger in diameter, for the other free end of the slide bush to terminate in a ring with a reduced inner diameter, and for the spring body to be disposed between the flange and the end face. The diameter of the rod roughly corresponds to the inner diameter of the ring.
A further suitable embodiment of the present invention provides for a collar with a circular cross section with an external diameter which roughly corresponds to the internal diameter of the slide bush. The free end face of the collar lies in the plane of the open end of the hollow cylinder. This achieves that in the driven-in piston, the spring bodies are disposed inside the control piston, while in the maximum driven-out position of the control piston, the spring bodies are disposed spaced from the end face of the control cylinder. The flange is disposed in its one operating position outside the control piston, and in its other operating position it reaches the proximity of the open end face of the control cylinder.
A particularly suitable embodiment of the present invention provides for at least two, suitably three, four, five or more control cylinders to disposed roughly symmetrically about the axis of rotation of the drive.
In the present invention it is particularly expedient if the spring body comprises one or more helical compression springs which have differing characteristic curves.